Metal casting operations have long employed the combination of a pattern set in a mold flask and with foundry sand compacted therearound to form the desired shape. In the normal operation, the pattern is then withdrawn from the sand and molten metal poured in the place previously occupied by the pattern which causes the metal to assume the shape of the pattern.
More recently, a modified system is employed wherein the pattern is made of a material which is converted to gas when contacted by the molten metal. With such patterns, it is not necessary to remove the pattern prior to casting and the result has been the ability to utilize more complicated patterns, i.e., patterns with more complex configurations such as internal passages, cavities, and the like.
In an effort to cause the foundry sand to fill cavities and the like in patterns, a system has been used wherein air is introduced into the bottom of the mold flask and flows upwardly through the sand with the intent being that the force of the moving air will in effect blow the sand into the cavities. While this method is effective for relatively simple patterns, it has not been completely effective where the pattern contains a number of internal passages, cavities, and the like.